To achieve higher circuit densities in most modern semiconductor devices the structural features formed in these semiconductor devices continue to shrink. With the lateral dimension scaling down much faster than the vertical dimension, high aspect ratio (HAR) structures are now prevalent in industry applications such as DRAM and vertical NAND. In modern semiconductor techniques, hardmasks are used for etching deep, high aspect ratio features that conventional photoresists cannot withstand. Among all the hardmask materials, boron-carbon films, such as a boron-carbon layer, have demonstrated superior patterning performance as compared to amorphous carbon when being used as an ashable hardmask during an etching process.
Recently developed boron-carbon films processed at high temperature (400° C. or higher) show even higher mass density and etch selectivity properties (3× the current best conventional hardmask film in market). However, boron-carbon films, especially deposited at high temperature, are not easily stripped or ashed. After depositing a high density hardmask layer on multiple substrates in a processing chamber, layers of unwanted material are deposited on various chamber components found within the processing chamber. These layers of unwanted material, which are also referred to herein as deposition residuals, accumulate on chamber components and surfaces of the processing chamber and eventually become a source of unwanted particles that will contaminate substrates that are subsequently processed in the processing chamber. To maintain the cleanliness of the processing chamber, a cleaning process has to be periodically performed after each or a number of substrates are processed in the processing chamber.
Conventional boron-doped carbon chamber cleaning processes have used remote plasma cleaning processes that have included fluorine-rich gaseous sources (e.g. NF3, CF4, SF6 and C2F6) or chlorine-rich source (Cl2, BCl3, or CCl4). However, for high temperature (T>400° C.) boron-carbon deposition processes such cleaning methods cannot be used, since the fluorine or chlorine containing cleaning gases will react with the aluminum (Al) containing heated chamber components found within the processing chamber. In one example, the surfaces of essential chamber components, such as the substrate heater, which is typically formed from aluminum nitride (AlN), can be rapidly etched due to the formation of aluminum fluoride (AlF3) or aluminum chloride (AlCl3) due to the fluorine-rich or chlorine-rich ambient conditions created during the chamber cleaning process. AlF3 is known to form at much faster rates at higher temperatures. At temperatures greater than 500° C., AlF3 sublimates and redeposits on chamber components and the chamber walls. The formation of AlF3 and AlCl3 during the cleaning process leads to Al/F/Cl contamination within the processing chamber and contributes to process drift over time and to unwanted particles during subsequent deposition processes performed in the processing chamber. Therefore, there is need for a new method of cleaning a processing chamber that selectively removes deposited boron-carbon layers from the various processing chamber components.